AUSTIN – A two-year-old white-tailed deer in a Medina County deer breeding facility has been confirmed positive for Chronic Wasting Disease (CWD). This is the first case of CWD detected in captive white-tailed deer in Texas. CWD was first detected in Texas in 2012 in free-ranging mule deer in the Hueco Mountains in far West Texas.

The Medina County tissue samples submitted by the breeder facility in early June as part of routine deer mortality surveillance revealed the presence of CWD during testing at the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) in College Station. The National Veterinary Services Laboratory in Ames, Iowa, confirmed the findings on Tuesday, June 30.

An epidemiological investigation to determine the extent of the disease, assess risks to Texas’ free ranging deer and protect the captive deer and elk breeding industry is being led by the Texas Animal Health Commission (TAHC), in coordination with the Texas Parks and Wildlife Department (TPWD) and U.S. Department of Agriculture’s Animal and Plant Health Inspection Service Veterinary Services (USDA/APHIS/VS).

Officials have taken immediate action to secure all cervids at the Medina County breeder facility with plans to conduct additional investigation for CWD. In addition, those breeder facilities that have received deer from the Medina County facility or shipped deer to that facility during the last two years are under movement restrictions and cannot move or release cervids at this time. TPWD is disallowing liberation of captive deer from all breeder facilities into the wild at this time pending further review. Additional measures to further minimize risk of CWD spreading into Texas’ free-ranging white-tailed deer herd, and to protect the captive deer breeding industry, will be considered.

“This is a terribly unfortunate development that we are committed to addressing as proactively, comprehensively, and expeditiously as possible. The health of our state’s wild and captive deer herds, as well as affiliated hunting, wildlife, and rural based economies, are vitally important to Texas hunters, communities, and landowners. As such, our primary objectives are to determine the source of the disease and to identify other deer breeding facilities and release sites that may have received deer from affected facilities,” said Carter Smith, TPWD Executive Director. “Working collaboratively with experts in the field we have developed protocols to address CWD, and our implementation efforts are already well under way.”

The TPWD and the TAHC CWD Management Plan will guide the State’s response to this incident. The plan was developed by the State’s CWD Task Force, which is comprised of deer and elk breeders, wildlife biologists, veterinarians and other animal-health experts from TPWD, TAHC, TVMDL, Department of State Health Services, Texas A&M College of Veterinary Medicine, and USDA.

Since 2002, the state has conducted surveillance throughout Texas for the disease. More than 34,000 samples collected from hunter-harvested and road kill deer have been tested for CWD.

Although animal health and wildlife officials cannot say how long or to what extent the disease has been present in the Medina County deer breeding facility, the breeder has had an active CWD surveillance program since 2006 with no positives detected until now.

“We are working with experts at the local, state and federal level, to determine the extent of this disease, and respond appropriately to limit further transmission,” said Dr. Andy Schwartz, TAHC Epidemiologist and Assistant Executive Director. “Strong public awareness and the continued support of the cervid industry is paramount to the success of controlling CWD in Texas.”

The disease was first recognized in 1967 in captive mule deer in Colorado. CWD has also been documented in captive and/or free-ranging deer in 23 states and 2 Canadian provinces. CWD among cervids is a progressive, fatal disease that commonly results in altered behavior as a result of microscopic changes made to the brain of affected animals. An animal may carry the disease for years without outward indication, but in the latter stages, signs may include listlessness, lowering of the head, weight loss, repetitive walking in set patterns, and a lack of responsiveness. To date there is no evidence that CWD poses a risk to humans or non-cervids. However, as a precaution, the U.S. Centers for Disease Control and the World Health Organization recommend not to consume meat from infected animals.

Chronic wasting disease (CWD) is a widespread and expanding prion disease in free-ranging and captive cervid species in North America. The zoonotic potential of CWD prions is a serious public health concern. Current literature generated with in vitro methods and in vivo animal models (transgenic mice, macaques and squirrel monkeys) reports conflicting results. The susceptibility of human CNS and peripheral organs to CWD prions remains largely unresolved. In our earlier bioassay experiments using several humanized transgenic mouse lines, we detected protease-resistant PrPSc in the spleen of two out of 140 mice that were intracerebrally inoculated with natural CWD isolates, but PrPSc was not detected in the brain of the same mice. Secondary passages with such PrPSc-positive CWD-inoculated humanized mouse spleen tissues led to efficient prion transmission with clear clinical and pathological signs in both humanized and cervidized transgenic mice. Furthermore, a recent bioassay with natural CWD isolates in a new humanized transgenic mouse line led to clinical prion infection in 2 out of 20 mice. ***These results indicate that the CWD prion has the potential to infect human CNS and peripheral lymphoid tissues and that there might be asymptomatic human carriers of CWD infection.

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***These results indicate that the CWD prion has the potential to infect human CNS and peripheral lymphoid tissues and that there might be asymptomatic human carriers of CWD infection.***

The propensity for trans-species prion transmission is related to the structural characteristics of the enciphering and heterologous PrP, but the exact mechanism remains mostly mysterious. Studies of the effects of primary or tertiary prion protein structures on trans-species prion transmission have relied primarily upon animal bioassays, making the influence of prion protein structure vs. host co-factors (e.g. cellular constituents, trafficking, and innate immune interactions) difficult to dissect. As an alternative strategy, we used real-time quakinginduced conversion (RT-QuIC) to investigate trans-species prion conversion.

To assess trans-species conversion in the RT-QuIC system, we compared chronic wasting disease (CWD) and bovine spongiform encephalopathy (BSE) prions, as well as feline CWD (fCWD) and feline spongiform encephalopathy (FSE). Each prion was seeded into each host recombinant PrP (full-length rPrP of white-tailed deer, bovine or feline). We demonstrated that fCWD is a more efficient seed for feline rPrP than for white-tailed deer rPrP, which suggests adaptation to the new host.

Conversely, FSE maintained sufficient BSE characteristics to more efficiently convert bovine rPrP than feline rPrP. Additionally, human rPrP was competent for conversion by CWD and fCWD. ***This insinuates that, at the level of protein:protein interactions, the barrier preventing transmission of CWD to humans is less robust than previously estimated.

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***This insinuates that, at the level of protein:protein interactions, the barrier preventing transmission of CWD to humans is less robust than previously estimated.***

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cwd environmental load factor in the land and surrounding plants and objects.

transportation of cervids and HUMANS from cwd zone should be regarded as a great risk factor, and environmental contamination.

PL1

Using in vitro prion replication for high sensitive detection of prions and prionlike proteins and for understanding mechanisms of transmission.

Claudio Soto

Mitchell Center for Alzheimer's diseases and related Brain disorders, Department of Neurology, University of Texas Medical School at Houston.

Prion and prion-like proteins are misfolded protein aggregates with the ability to selfpropagate to spread disease between cells, organs and in some cases across individuals. I n T r a n s m i s s i b l e s p o n g i f o r m encephalopathies (TSEs), prions are mostly composed by a misfolded form of the prion protein (PrPSc), which propagates by transmitting its misfolding to the normal prion protein (PrPC). The availability of a procedure to replicate prions in the laboratory may be important to study the mechanism of prion and prion-like spreading and to develop high sensitive detection of small quantities of misfolded proteins in biological fluids, tissues and environmental samples. Protein Misfolding Cyclic Amplification (PMCA) is a simple, fast and efficient methodology to mimic prion replication in the test tube. PMCA is a platform technology that may enable amplification of any prion-like misfolded protein aggregating through a seeding/nucleation process. In TSEs, PMCA is able to detect the equivalent of one single molecule of infectious PrPSc and propagate prions that maintain high infectivity, strain properties and species specificity. Using PMCA we have been able to detect PrPSc in blood and urine of experimentally infected animals and humans affected by vCJD with high sensitivity and specificity. Recently, we have expanded the principles of PMCA to amplify amyloid-beta (A&#946;) and alphasynuclein (&#945;-syn) aggregates implicated in Alzheimer's and Parkinson's diseases, respectively. Experiments are ongoing to study the utility of this technology to detect A&#946; and &#945;-syn aggregates in samples of CSF and blood from patients affected by these diseases.

***Recently, we have been using PMCA to study the role of environmental prion contamination on the horizontal spreading of TSEs. These experiments have focused on the study of the interaction of prions with plants and environmentally relevant surfaces. Our results show that plants (both leaves and roots) bind tightly to prions present in brain extracts and excreta (urine and feces) and retain even small quantities of PrPSc for long periods of time. Strikingly, ingestion of prioncontaminated leaves and roots produced disease with a 100% attack rate and an incubation period not substantially longer than feeding animals directly with scrapie brain homogenate. Furthermore, plants can uptake prions from contaminated soil and transport them to different parts of the plant tissue (stem and leaves). Similarly, prions bind tightly to a variety of environmentallyrelevant surfaces, including stones, wood, metals, plastic, glass, cement, etc. Prion contaminated surfaces efficiently transmit prion disease when these materials were directly injected into the brain of animals and strikingly when the contaminated surfaces were just placed in the animal cage. These findings demonstrate that environmental materials can efficiently bind infectious prions and act as carriers of infectivity, suggesting that they may play an important role in the horizontal transmission of the disease.

Since its invention 13 years ago, PMCA has helped to answer fundamental questions of prion propagation and has broad applications in research areas including the food industry, blood bank safety and human and veterinary disease diagnosis.

Prion diseases (PD) are the unique neurodegenerative proteinopathies reputed to be transmissible under field conditions since decades. The transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that an animal PD might be zoonotic under appropriate conditions. Contrarily, in the absence of obvious (epidemiological or experimental) elements supporting a transmission or genetic predispositions, PD, like the other proteinopathies, are reputed to occur spontaneously (atpical animal prion strains, sporadic CJD summing 80% of human prion cases). Non-human primate models provided the first evidences supporting the transmissibiity of human prion strains and the zoonotic potential of BSE. Among them, cynomolgus macaques brought major information for BSE risk assessment for human health (Chen, 2014), according to their phylogenetic proximity to humans and extended lifetime. We used this model to assess the zoonotic potential of other animal PD from bovine, ovine and cervid origins even after very long silent incubation periods. *** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period, ***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold longe incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014), ***is the third potentially zoonotic PD (with BSE and L-type BSE), ***thus questioning the origin of human sporadic cases. We will present an updated panorama of our different transmission studies and discuss the implications of such extended incubation periods on risk assessment of animal PD for human health.

Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie prions remains unknown. Mice genetically engineered to overexpress the human &#8203;prion protein (tgHu) have emerged as highly relevant models for gauging the capacity of prions to transmit to humans. These models can propagate human prions without any apparent transmission barrier and have been used used to confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie prions transmit to several tgHu mice models with an efficiency comparable to that of cattle BSE. ***The serial transmission of different scrapie isolates in these mice led to the propagation of prions that are phenotypically identical to those causing sporadic CJD (sCJD) in humans. ***These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.

Prions circulate in the blood of prion-infected hosts, including humans with variant Creutzfeldt- Jakob disease. Determining the parameters of blood-borne prions during the long asymptomatic phase of disease characteristic of all prion diseases has been a long-standing problem in prion biology. Elder et. al (p. 7421–7424) have demonstrated amyloid formation, a biomarker for prions, in the blood of prion-infected rodent and cervid hosts as early as 15 minutes post-mucosal or -intravenous infection. This prionemia persists throughout the disease course, indicating a role for hematogenous prions throughout the preclinical stage of illness.

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UPDATED June 20, 2015 further into this study ;

***This is the first report of the detection of PrPC-CCA in the blood of animals within minutes of exposure to TSE inoculum. The use of PrPC-CCA to detect prions in tissues and bodily fluids of TSE-infected hosts has been shown to be as sensitive as a bioassay and has provided insight into a variety of prion diseases (15–18). The immediate detection of the point-source inoculum was seen following exposure to mucosal surfaces in the nose and gut; the same immediate detection of PrPC-CCA was seen following i.v. injection. This immediate detection indicates that the mucosae of the nasal cavity and the gut provide an inefficient anatomical barrier to prion entry—i.e., exposure to the mucosal surfaces does not differ significantly, in terms of temporal systemic spread, from injection directly into blood. These data, along with reports from Kincaid et al. (19) and Jeffrey et al. (20), demonstrate that mucosal surfaces are not capable of preventing the near-immediate passage of the inoculum into underlying lamina propria and blood. The absence of an efficient mucosal barrier to prion infection has significant implications for the pathogenesis of prion diseases. *** In addition, there are experimental and safety concerns, including the consideration that the blood of any animal exposed to prions may immediately contain prions.

• If the epidemiological investigation determines that the herd was not commingled with an animal from the CWD-positive herd, the herd will be reinstated to its former status, and the time spent in Suspended status be counted in its herd status.

• Animals are commingled if they have direct contact with each other, have less than 10 feet of physical separation, or share equipment, pasture, or water sources/watershed.

Where are the links to show who is trying to find the source of how this disease got to that ranch in Medina County, in the middle of Texas? That would seem to be pretty important for all those concerned about stopping the spread of it to new and unrelated locations.

• If the epidemiological investigation determines that the herd was not commingled with an animal from the CWD-positive herd, the herd will be reinstated to its former status, and the time spent in Suspended status be counted in its herd status.

• Animals are commingled if they have direct contact with each other, have less than 10 feet of physical separation, or share equipment, pasture, or water sources/watershed.

They are planning on bypassing these.

_________________________
"I cant wait to see if he plays this week, and if he does if he can actually break 50 percent completion ratio. Haha or maybe even throw for 200 yards. Possibly break a QB rating of 75." - Texas Tatonka www.bigironranchadventures.com

• If the epidemiological investigation determines that the herd was not commingled with an animal from the CWD-positive herd, the herd will be reinstated to its former status, and the time spent in Suspended status be counted in its herd status.

• Animals are commingled if they have direct contact with each other, have less than 10 feet of physical separation, or share equipment, pasture, or water sources/watershed.

Where are the links to show who is trying to find the source of how this disease got to that ranch in Medina County, in the middle of Texas? That would seem to be pretty important for all those concerned about stopping the spread of it to new and unrelated locations.

Where are the links to show who is trying to find the source of how this disease got to that ranch in Medina County, in the middle of Texas? That would seem to be pretty important for all those concerned about stopping the spread of it to new and unrelated locations.

Yelp!!!

They are not interested in "stopping the spread" of CWD. They are interested in destroying the industry.

In fact, it's like it's a "timed event" because they see live testing being developed and they need to get their dirty work done before live testing hobbles their agenda.

That's the only logical reason they refused to allow the deer to be put into a research program.

Edited by therancher (07/10/1511:16 PM)

_________________________
"I cant wait to see if he plays this week, and if he does if he can actually break 50 percent completion ratio. Haha or maybe even throw for 200 yards. Possibly break a QB rating of 75." - Texas Tatonka www.bigironranchadventures.com

It is mid July. How does this case of CWD affect other HF ranches in Texas that release bucks from breeder area to hunting area? Are they all under a restriction until TPWD traces if any deer were sold or transferred to other Texas ranches?

There is currently a moratorium on all transfers. I posted the protocol on the other CWD thread. It's a pretty tedious read but it leaves the option open for later in the year that transfers could resume.

Nobody I know expects tpwd to be in any hurrys though. Scuttlebutt from within the agency is that this is the opportunity they've been hoping for and that they are determined to cripple the industry.

_________________________
"I cant wait to see if he plays this week, and if he does if he can actually break 50 percent completion ratio. Haha or maybe even throw for 200 yards. Possibly break a QB rating of 75." - Texas Tatonka www.bigironranchadventures.com

Where are the links to show who is trying to find the source of how this disease got to that ranch in Medina County, in the middle of Texas? That would seem to be pretty important for all those concerned about stopping the spread of it to new and unrelated locations.

Yelp!!!

They are not interested in "stopping the spread" of CWD. They are interested in destroying the industry.

In fact, it's like it's a "timed event" because they see live testing being developed and they need to get their dirty work done before live testing hobbles their agenda.

That's the only logical reason they refused to allow the deer to be put into a research program.

I don't think that's the case at all, in my opinion. here's why.

what the TAHC and TPWD are so concerned about, is the longer you fool around with one cwd positive, and let that one positive cwd case turn into another, and then another, while litigating on what to do or not do, you risk load factor into the environment, and further spreading to other animals. again, a perfect example, were all those healthy deer in Iowa, that had a case of CWD. while all that mess was in limbo, that herd became 79.8 % infection rate over a longer period of time. but everyone thought those were all healthy deer. there was talk of cutting the fences and letting them all go free to save the healthy _looking_ deer. I say kill all of them now, test all of them now, and then incinerate. scorched earth policy. it's the only way until more is known about the cwd tse prion agent. why ignore what we already know, and risk further spreading of the cwd TSE agent? only one reason... MONEY $$$

terry

references

*** We conclude that TSE infectivity is likely to survive burial for long time periods with minimal loss of infectivity and limited movement from the original burial site. However PMCA results have shown that there is the potential for rainwater to elute TSE related material from soil which could lead to the contamination of a wider area. These experiments reinforce the importance of risk assessment when disposing of TSE risk materials.

*** The results show that even highly diluted PrPSc can bind efficiently to polypropylene, stainless steel, glass, wood and stone and propagate the conversion of normal prion protein. For in vivo experiments, hamsters were ic injected with implants incubated in 1% 263K-infected brain homogenate. Hamsters, inoculated with 263K-contaminated implants of all groups, developed typical signs of prion disease, whereas control animals inoculated with non-contaminated materials did not.

PRION 2014 CONFERENCE

CHRONIC WASTING DISEASE CWD

A FEW FINDINGS ;

Conclusions. To our knowledge, this is the first established experimental model of CWD in TgSB3985. We found evidence for co-existence or divergence of two CWD strains adapted to Tga20 mice and their replication in TgSB3985 mice. Finally, we observed phenotypic differences between cervid-derived CWD and CWD/Tg20 strains upon propagation in TgSB3985 mice. Further studies are underway to characterize these strains.

We conclude that TSE infectivity is likely to survive burial for long time periods with minimal loss of infectivity and limited movement from the original burial site. However PMCA results have shown that there is the potential for rainwater to elute TSE related material from soil which could lead to the contamination of a wider area. These experiments reinforce the importance of risk assessment when disposing of TSE risk materials.

The results show that even highly diluted PrPSc can bind efficiently to polypropylene, stainless steel, glass, wood and stone and propagate the conversion of normal prion protein. For in vivo experiments, hamsters were ic injected with implants incubated in 1% 263K-infected brain homogenate. Hamsters, inoculated with 263K-contaminated implants of all groups, developed typical signs of prion disease, whereas control animals inoculated with non-contaminated materials did not.

Our data establish that meadow voles are permissive to CWD via peripheral exposure route, suggesting they could serve as an environmental reservoir for CWD. Additionally, our data are consistent with the hypothesis that at least two strains of CWD circulate in naturally-infected cervid populations and provide evidence that meadow voles are a useful tool for CWD strain typing.

Conclusion. CWD prions are shed in saliva and urine of infected deer as early as 3 months post infection and throughout the subsequent >1.5 year course of infection. In current work we are examining the relationship of prionemia to excretion and the impact of excreted prion binding to surfaces and particulates in the environment.

Conclusion. CWD prions (as inferred by prion seeding activity by RT-QuIC) are shed in urine of infected deer as early as 6 months post inoculation and throughout the subsequent disease course. Further studies are in progress refining the real-time urinary prion assay sensitivity and we are examining more closely the excretion time frame, magnitude, and sample variables in relationship to inoculation route and prionemia in naturally and experimentally CWD-infected cervids.

Conclusions. Our results suggested that the odds of infection for CWD is likely controlled by areas that congregate deer thus increasing direct transmission (deer-to-deer interactions) or indirect transmission (deer-to-environment) by sharing or depositing infectious prion proteins in these preferred habitats. Epidemiology of CWD in the eastern U.S. is likely controlled by separate factors than found in the Midwestern and endemic areas for CWD and can assist in performing more efficient surveillance efforts for the region.

Conclusions. During the pre-symptomatic stage of CWD infection and throughout the course of disease deer may be shedding multiple LD50 doses per day in their saliva. CWD prion shedding through saliva and excreta may account for the unprecedented spread of this prion disease in nature.

Resistant prions in the environment have been the sword of Damocles for scrapie control and eradication. Attempts to establish which physical and chemical agents could be applied to inactivate or moderate scrapie infectivity were initiated in the 1960s and 1970s,with the first study of this type focusing on the effect of heat treatment in reducing prion infectivity (Hunter and Millson 1964). Nowadays, most of the chemical procedures that aim to inactivate the prion protein are based on the method developed by Kimberlin and collaborators (1983). This procedure consists of treatment with 20,000 parts per million free chlorine solution, for a minimum of one hour, of all surfaces that need to be sterilised (in laboratories, lambing pens, slaughterhouses, and so on). Despite this, veterinarians and farmers may still ask a range of questions, such as ‘Is there an official procedure published somewhere?’ and ‘Is there an international organisation which recommends and defines the exact method of scrapie decontamination that must be applied?’

From a European perspective, it is difficult to find a treatment that could be applied, especially in relation to the disinfection of surfaces in lambing pens of affected flocks. A 999/2001 EU regulation on controlling spongiform encephalopathies (European Parliament and Council 2001) did not specify a particular decontamination measure to be used when an outbreak of scrapie is diagnosed. There is only a brief recommendation in Annex VII concerning the control and eradication of transmissible spongiform encephalopathies (TSE s).

Chapter B of the regulation explains the measures that must be applied if new caprine animals are to be introduced to a holding where a scrapie outbreak has previously been diagnosed. In that case, the statement indicates that caprine animals can be introduced ‘provided that a cleaning and disinfection of all animal housing on the premises has been carried out following destocking’.

Issues around cleaning and disinfection are common in prion prevention recommendations, but relevant authorities, veterinarians and farmers may have difficulties in finding the specific protocol which applies. The European Food and Safety Authority (EFSA ) published a detailed report about the efficacy of certain biocides, such as sodium hydroxide, sodium hypochlorite, guanidine and even a formulation of copper or iron metal ions in combination with hydrogen peroxide, against prions (EFSA 2009). The report was based on scientific evidence (Fichet and others 2004, Lemmer and others 2004, Gao and others 2006, Solassol and others 2006) but unfortunately the decontamination measures were not assessed under outbreak conditions.

The EFSA Panel on Biological Hazards recently published its conclusions on the scrapie situation in the EU after 10 years of monitoring and control of the disease in sheep and goats (EFSA 2014), and one of the most interesting findings was the Icelandic experience regarding the effect of disinfection in scrapie control. The Icelandic plan consisted of: culling scrapie-affected sheep or the whole flock in newly diagnosed outbreaks; deep cleaning and disinfection of stables, sheds, barns and equipment with high pressure washing followed by cleaning with 500 parts per million of hypochlorite; drying and treatment with 300 ppm of iodophor; and restocking was not permitted for at least two years. Even when all of these measures were implemented, scrapie recurred on several farms, indicating that the infectious agent survived for years in the environment, even as many as 16 years after restocking (Georgsson and others 2006).

In the rest of the countries considered in the EFSA (2014) report, recommendations for disinfection measures were not specifically defined at the government level. In the report, the only recommendation that is made for sheep is repopulation with sheep with scrapie-resistant genotypes. This reduces the risk of scrapie recurrence but it is difficult to know its effect on the infection.

Until the EFSA was established (in May 2003), scientific opinions about TSE s were provided by the Scientific Steering Committee (SSC) of the EC, whose advice regarding inactivation procedures focused on treating animal waste at high temperatures (150°C for three hours) and high pressure alkaline hydrolysis (SSC 2003). At the same time, the TSE Risk Management Subgroup of the Advisory Committee on Dangerous Pathogens (ACDP) in the UK published guidance on safe working and the prevention of TSE infection. Annex C of the ACDP report established that sodium hypochlorite was considered to be effective, but only if 20,000 ppm of available chlorine was present for at least one hour, which has practical limitations such as the release of chlorine gas, corrosion, incompatibility with formaldehyde, alcohols and acids, rapid inactivation of its active chemicals and the stability of dilutions (ACDP 2009).

In an international context, the World Organisation for Animal Health (OIE) does not recommend a specific disinfection protocol for prion agents in its Terrestrial Code or Manual. Chapter 4.13 of the Terrestrial Code, General recommendations on disinfection and disinsection (OIE 2014), focuses on foot-and-mouth disease virus, mycobacteria and Bacillus anthracis, but not on prion disinfection. Nevertheless, the last update published by the OIE on bovine spongiform encephalopathy (OIE 2012) indicates that few effective decontamination techniques are available to inactivate the agent on surfaces, and recommends the removal of all organic material and the use of sodium hydroxide, or a sodium hypochlorite solution containing 2 per cent available chlorine, for more than one hour at 20ºC.

The World Health Organization outlines guidelines for the control of TSE s, and also emphasises the importance of mechanically cleaning surfaces before disinfection with sodium hydroxide or sodium hypochlorite for one hour (WHO 1999).

Finally, the relevant agencies in both Canada and the USA suggest that the best treatments for surfaces potentially contaminated with prions are sodium hydroxide or sodium hypochlorite at 20,000 ppm. This is a 2 per cent solution, while most commercial household bleaches contain 5.25 per cent sodium hypochlorite. It is therefore recommended to dilute one part 5.25 per cent bleach with 1.5 parts water (CDC 2009, Canadian Food Inspection Agency 2013).

So what should we do about disinfection against prions? First, it is suggested that a single protocol be created by international authorities to homogenise inactivation procedures and enable their application in all scrapie-affected countries. Sodium hypochlorite with 20,000 ppm of available chlorine seems to be the procedure used in most countries, as noted in a paper summarised on p 99 of this issue of Veterinary Record (Hawkins and others 2015). But are we totally sure of its effectiveness as a preventive measure in a scrapie outbreak? Would an in-depth study of the recurrence of scrapie disease be needed?

What we can conclude is that, if we want to fight prion diseases, and specifically classical scrapie, we must focus on the accuracy of diagnosis, monitoring and surveillance; appropriate animal identification and control of movements; and, in the end, have homogeneous and suitable protocols to decontaminate and disinfect lambing barns, sheds and equipment available to veterinarians and farmers. Finally, further investigations into the resistance of prion proteins in the diversity of environmental surfaces are required.

1Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK 2School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK 3ADAS UK, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK E-mail for correspondence: ben.maddison@adas.co.uk Abstract Scrapie of sheep/goats and chronic wasting disease of deer/elk are contagious prion diseases where environmental reservoirs are directly implicated in the transmission of disease. In this study, the effectiveness of recommended scrapie farm decontamination regimens was evaluated by a sheep bioassay using buildings naturally contaminated with scrapie. Pens within a farm building were treated with either 20,000 parts per million free chorine solution for one hour or were treated with the same but were followed by painting and full re-galvanisation or replacement of metalwork within the pen. Scrapie susceptible lambs of the PRNP genotype VRQ/VRQ were reared within these pens and their scrapie status was monitored by recto-anal mucosa-associated lymphoid tissue. All animals became infected over an 18-month period, even in the pen that had been subject to the most stringent decontamination process. These data suggest that recommended current guidelines for the decontamination of farm buildings following outbreaks of scrapie do little to reduce the titre of infectious scrapie material and that environmental recontamination could also be an issue associated with these premises.

SNIP...

Discussion

Thorough pressure washing of a pen had no effect on the amount of bioavailable scrapie infectivity (pen B). The routine removal of prions from surfaces within a laboratory setting is treatment for a minimum of one hour with 20,000 ppm free chlorine, a method originally based on the use of brain macerates from infected rodents to evaluate the effectiveness of decontamination (Kimberlin and others 1983). Further studies have also investigated the effectiveness of hypochlorite disinfection of metal surfaces to simulate the decontamination of surgical devices within a hospital setting. Such treatments with hypochlorite solution were able to reduce infectivity by 5.5 logs to lower than the sensitivity of the bioassay used (Lemmer and others 2004). Analogous treatment of the pen surfaces did not effectively remove the levels of scrapie infectivity over that of the control pens, indicating that this method of decontamination is not effective within a farm setting. This may be due to the high level of biological matrix that is present upon surfaces within the farm environment, which may reduce the amount of free chlorine available to inactivate any infectious prion. Remarkably 1/5 sheep introduced into pen D had also became scrapie positive within nine months, with all animals in this pen being RAMALT positive by 18 months of age. Pen D was no further away from the control pen (pen A) than any of the other pens within this barn. Localised hot spots of infectivity may be present within scrapie-contaminated environments, but it is unlikely that pen D area had an amount of scrapie contamination that was significantly different than the other areas within this building. Similarly, there were no differences in how the biosecurity of pen D was maintained, or how this pen was ventilated compared with the other pens. This observation, perhaps, indicates the slower kinetics of disease uptake within this pen and is consistent with a more thorough prion removal and recontamination. These observations may also account for the presence of inadvertent scrapie cases within other studies, where despite stringent biosecurity, control animals have become scrapie positive during challenge studies using barns that also housed scrapie-affected animals (Ryder and others 2009). The bioassay data indicate that the exposure of the sheep to a farm environment after decontamination efforts thought to be effective in removing scrapie is sufficient for the animals to become infected with scrapie. The main exposure routes within this scenario are likely to be via the oral route, during feeding and drinking, and respiratory and conjunctival routes. It has been demonstrated that scrapie infectivity can be efficiently transmitted via the nasal route in sheep (Hamir and others 2008), as is the case for CWD in both murine models and in white-tailed deer (Denkers and others 2010, 2013). Recently, it has also been demonstrated that CWD prions presented as dust when bound to the soil mineral montmorillonite can be infectious via the nasal route (Nichols and others 2013). When considering pens C and D, the actual source of the infectious agent in the pens is not known, it is possible that biologically relevant levels of prion survive on surfaces during the decontamination regimen (pen C). With the use of galvanising and painting (pen D) covering and sealing the surface of the pen, it is possible that scrapie material recontaminated the pens by the movement of infectious prions contained within dusts originating from other parts of the barn that were not decontaminated or from other areas of the farm.

Given that scrapie prions are widespread on the surfaces of affected farms (Maddison and others 2010a), irrespective of the source of the infectious prions in the pens, this study clearly highlights the difficulties that are faced with the effective removal of environmentally associated scrapie infectivity. This is likely to be paralleled in CWD which shows strong similarities to scrapie in terms of both the dissemination of prions into the environment and the facile mode of disease transmission. These data further contribute to the understanding that prion diseases can be highly transmissible between susceptible individuals not just by direct contact but through highly stable environmental reservoirs that are refractory to decontamination.

The presence of these environmentally associated prions in farm buildings make the control of these diseases a considerable challenge, especially in animal species such as goats where there is lack of genetic resistance to scrapie and, therefore, no scope to re-stock farms with animals that are resistant to scrapie.

Ovine scrapie shows considerable horizontal transmission, yet the routes of transmission and specifically the role of fomites in transmission remain poorly defined. Here we present biochemical data demonstrating that on a scrapie-affected sheep farm, scrapie prion contamination is widespread. It was anticipated at the outset that if prions contaminate the environment that they would be there at extremely low levels, as such the most sensitive method available for the detection of PrPSc, serial Protein Misfolding Cyclic Amplification (sPMCA), was used in this study. We investigated the distribution of environmental scrapie prions by applying ovine sPMCA to samples taken from a range of surfaces that were accessible to animals and could be collected by use of a wetted foam swab. Prion was amplified by sPMCA from a number of these environmental swab samples including those taken from metal, plastic and wooden surfaces, both in the indoor and outdoor environment. At the time of sampling there had been no sheep contact with these areas for at least 20 days prior to sampling indicating that prions persist for at least this duration in the environment. These data implicate inanimate objects as environmental reservoirs of prion infectivity which are likely to contribute to disease transmission.

*** After a natural route of exposure, 100% of WTD were susceptible to scrapie.

Deer developed clinical signs of wasting and mental depression and were necropsied from 28 to 33 months PI. Tissues from these deer were positive for PrPSc by IHC and WB. Similar to IC inoculated deer, samples from these deer exhibited two different molecular profiles: samples from obex resembled CWD whereas those from cerebrum were similar to the original scrapie inoculum. On further examination by WB using a panel of antibodies, the tissues from deer with scrapie exhibit properties differing from tissues either from sheep with scrapie or WTD with CWD. Samples from WTD with CWD or sheep with scrapie are strongly immunoreactive when probed with mAb P4, however, samples from WTD with scrapie are only weakly immunoreactive. In contrast, when probed with mAb’s 6H4 or SAF 84, samples from sheep with scrapie and WTD with CWD are weakly immunoreactive and samples from WTD with scrapie are strongly positive. This work demonstrates that WTD are highly susceptible to sheep scrapie, but on first passage, scrapie in WTD is differentiable from CWD.

Where are the links to show who is trying to find the source of how this disease got to that ranch in Medina County, in the middle of Texas? That would seem to be pretty important for all those concerned about stopping the spread of it to new and unrelated locations.

Yelp!!!

They are not interested in "stopping the spread" of CWD. They are interested in destroying the industry.

In fact, it's like it's a "timed event" because they see live testing being developed and they need to get their dirty work done before live testing hobbles their agenda.

That's the only logical reason they refused to allow the deer to be put into a research program.

"I say kill all of them now, test all of them now, and then incinerate. scorched earth policy. it's the only way until more is known about the cwd tse prion agent. why ignore what we already know, and risk further spreading of the cwd TSE agent? only one reason... MONEY $$$"

No, not money, valid valuable scientific study. Exactly how do you "learn more about the cwd prion" if you refuse to authorize research??

You have one deer that tested positive (possibly the only one in the group). In a controlled, closed environment. It's the perfect lab. Re-enforce the security, or move all the animals to an even more secure facility. And develop live testing, study CWD long term and short term. And determine how CWD got in that pen.

There is no excuse other than, you and TPWD/TAHC want to destroy an industry, and strip personal control from the individual and assign it to the state.

Edited by therancher (07/11/1504:29 PM)

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